Hand-held tools such as wallpaper strippers and crease removers must be capable of effective use in a number of different orientations and, with some prior proposals, it is found that in certain orientations hot water might possibly be ejected from the steam nozzles of the tool. This reduces the effectiveness of the tool and may possibly be hazardous to the user. It is also found that, in prior proposals, because of the impurities present in water there is a tendency for particles to be deposited in the steam passageways and to pass to the steam nozzles where the particles may block the nozzles and again this may reduce the effectiveness of the tool.
Steam generators for wallpaper strippers are described in U.S. Pat. Nos. 4,990,745 and 4,857,703, the disclosures of both of which are hereby incorporated by reference. These generators comprise a body of heat conductive material with an electric heating element housed within the body. A number of passageways are formed within the body, extending from a water inlet to outlets for steam. Steam is generated on one side only of the generator, and the maximum nominal rate of steam production which can be obtained using generators of this type to obtain steam with very few or no water droplets is about 25 cc per minute. Ideally, the water should be changed completely to steam.
In order to increase the rate of steam production significantly above the rate of approximately 25 cc per minute, using the steam generators of the above U.S. Patents, two alternative possible approaches appear possible.
One approach which might be considered is to attempt to increase the path length, and hence the time for which the water is in contact with the heating element, by making the tracks smaller and more convoluted. However, since the water contains dissolved and suspected impurities which are precipitated out by boiling, the problem arises that particles will build up in the tracks which become restricted, or the heat transfer becomes less efficient. This by itself then is not a practical solution.
In an alternative approach, consideration could be given to increasing the temperature of the casting. This would have the result of increasing the volume of steam production, but would risk over-heating of the housing. The housing is preferably made from a plastics material; the available type of thermostat used in wallpaper strippers, etc., would then be set to operate at a nominal temperature of 160 degrees C., with a tolerance of .+-.7 degrees C., and this is around the practical temperature limit for a plastics housing.